1. Field of the Invention
Invention relates to a method and apparatus for discharging fuel and oxidant from a nozzle in a fashion that forms a fishtail or fan-shaped flame which produces uniform heat distribution and relatively high radiative heat transmission.
2. Description of Prior Art
Combustion technology involving 100% oxygen-fuel is relatively new in glass melting applications. Many conventional burners use a cylindrical burner geometry wherein fuel and oxidant are discharged from a cylindrical nozzle, such as a cylindrical refractory burner block. Such cylindrical discharge nozzles produce a flame profile that diverges at an included angle of 20.degree. to 25.degree., in a generally conical shape. Conventional burners that produce generally conical flames create undesirable hot-spots in a furnace. The hot-spots result in furnace refractory damage, particularly to furnace crowns and sidewalls which are opposite the flame. Such conventional burners also result in increased batch volatilization and uncontrolled emissions of nitrogen oxides, sulfur oxides and process particulates.
To overcome some of the problems associated with such designs, conventional burners have incorporated low momentum flow wherein relatively lower oxygen and fuel velocities are used to create relatively lower momentum flames. Such lower velocities and thus lower momentums result in longer flames and increased load coverage. However, a flame lofting problem occurs at such relatively low velocities and thus causes undesirable effects.
Some conventional burners employ a staggered firing arrangement in an attempt to improve effective load coverage, particularly with the use of conical expansion of individual flames. However, the staggered firing arrangement often creates undesirable cold regions in pocket areas between adjacent burners. To overcome such problem, other conventional burners have attempted to increase the number of flames by using more burners. However, increasing the number of burners significantly increases installation and operation costs.
U.S. Pat. No. 5,217,363 teaches an air-cooled oxygen gas burner having a body which forms three concentric metal tubes supported in a cylindrical housing and positioned about a conical bore in a refractory sidewall of a furnace. The three concentric tubes can be adjusted with respect to each other, to define a nozzle with annular openings of variable size for varying the shape of a flame produced by a mixture of fuel, oxygen and air. The air is fed through an outer chamber, for cooling the concentric tube assembly and the furnace refractory positioned about the burner nozzle.
U.S. Pat. Nos. 5,256,058 and 5,346,390 disclose a method and apparatus for generating an oxy-fuel flame. The oxy-fuel flame is produced in a concentric orifice burner and thus results in a generally cylindrical flame. A fuel-rich flame is shielded within a fuel-lean or oxygen-rich flame. The flame shielding is controlled in order to achieve a two-phase turbulent diffusion flame in a precombustor, in order to prevent aspiration of corrosive species and also to reduce nitrogen oxides formation.
U.S. Pat. No. 5,076,779 discloses a combustion burner operating with segregated combustion zones. Separate oxidant mixing zones and fuel reaction zones are established in a combustion zone, in order to dilute oxidant and also to combust fuel under conditions which reduce nitrogen oxides formation.
It is apparent that there is a need for an oxy-fuel burner which can be used in high-temperature furnaces, such as glass melting furnaces, that provides uniform heat distribution, reduced undesirable emissions, such as nitrogen oxides and sulfur oxides, and which produces a highly radiative and luminous flame.